BIOL 161 part two plant biology

Alnternation of generations

is the life cycle that land plants use to alternate between two multicellular stages:

what are is one of the two main stages for the altenration of generations

• Sporophyte (2n) – Diploid

  • Produces haploid spores via meiosis

  • Dominant stage in vascular plants (like ferns, gymnosperms, and angiosperms)

name the other stage of the alternation of generations (gametophyte)

• Gametophyte (n) – Haploid

  • Develops from a spore via mitosis

  • Produces haploid gametes (egg & sperm) via mitosis

  • Dominant stage in non-vascular plants (like mosses)

homospory

all spres are the same gametophutes with respect to sex expression

bisexual: both sperm and egg are produced by gametophutes

heterospory

two different types of spores

gametophytes are specialized with respect to sexual expression

Unisexual (separate male & female)

two kinds: microspore & megaspore

Major caldes of seedless land plants

liverwords (hep.)

homworts(anth.)

mosses (bryo.)

Liverworts nonvascular

leafy, thalloid

short sporophytes

asexual reprod.

Homworts land plant

nonvasular seedless plants

simple stomatoa in thallus

gameotphyes similar to liverworts

intermeidate growth in sporocuyte

homoplasy life cycle

mosses

apical cell divison

cells spealized fpr transporation

Mitosis

creates sperm and eggs

Meosis

creates spores

For seedless plants the gametopjute is

independent from the sporocyte

secondayr growth

lateral meristem; gives us trees

80 percent of terrestrial biomass

tallest and oldest lviing organsim

plants contiue to grow

megagametophyte

Mega: female, megaspore

• Produces the egg cell, in ovule

• 1 megaspore → mitosis → megagametophyte (embryo sac) → egg

microgametophyte

male

• It develops from a microspore

• Produces the sperm cells

• In flowering plants, it's the pollen grain

1 microspore → mitosis → microgametophyte (pollen grain) → sperm cells

In seed plants:

they are well protected and already have a well delvoped emrbyo and are viable for years to coem

Angiosperm

Angiosperms (Flowering plants)

• Have flowers

• Make fruits with seeds inside

• Use animals (like bees or birds) for pollination

• Most plants today are angiosperms

enclosed seed

double fertilization

Gymnosperm (Vascular seeded plant)

• No flowers, no fruit

• Make cones instead

• Seeds are naked (not in fruit)

• Use wind to spread pollen

naked seed

Flowers

modified leaves

central access

stamen: male

pistil: female

antheridia

archegonia

archegonia

male

female

Seedless vascular plants:

Sporophtye and gametophyte independent

Vascular seed plants

Gametophyte dependent on sporophyte

bryophytes (liverworts, moss, hornworts)

nonvbasular plants

like moist

reproduce via spores

haploid gametophyte stage is dominant in the life cycle